It is now conventional to manufacture beverage containers from aluminum alloys. An aluminum alloy sheet stock is first blanked into a circular configuration and then cupped. The side wall are ironed by passing the cup through a series of dies having diminishing bores. The dies thus produce an ironing effect which lengthens the sidewall to produce a can body thinner in dimension than its bottom.
Thus, formability is a key characteristic of aluminum alloy to be used in manufacturing cans. Such cans are most frequently produced from aluminum alloys of the 3000 series. Such aluminum alloys contain alloy elements of both magnesium and manganese. In general, the amount of manganese and magnesium used in can body stock is about 1% by weight.
In the manufacture of complete "two-piece" aluminum beverage containers, it has been the practice in the industry to separately form the bodies, top ends and tabs. Such ends and tabs are then shipped to the filler of the beverage can and applied once the containers have been filled. The requirements for can ends and tabs are generally quite different than those for can bodies. In general, greater strength is required for can ends and tabs, and that requirement for greater strength has dictated that such can ends and tabs be fabricated from a aluminum alloy different from that used in can bodies. One such alloy commonly used is alloy AA5182, which contains relatively high amounts of magnesium to provide the added strength and formability necessary for can ends and tabs. AA5182 typically contains magnesium in an amount of about 4.4% by weight, thus adding to the cost of the alloy for can ends and tabs.
Alloys from the 3000 series, such as AA3104, have been proposed in the fabrication of can ends and tabs. When can ends are fabricated from AA3104 they require a greater thickness and thus are more expensive because such alloys generally have diminished strength and formability as compared to AA5182.